A valid consent must fulfil the following three essential components: 

•    Disclosure: Provision of relevant information by the clinician and its comprehension by the patient.•    Capacity: Ability of the patient to understand the relevant information and to appreciate those consequences of his or her decision that might reasonably be foreseen.•    Voluntariness: Right of the patient to come to a decision freely, without force, coercion or manipulation.

Consent is not valid if it is given under fear of injury/intimidation, misconception or misrepresentation of facts is an invalid consent. 1 

Blanket consent is not legal. This denotes that the consent given by the patient for a diagnostic procedure cannot be extended to a therapeutic procedure unless there is a potentially life-threatening emergency. 

This was also the position held by the Supreme Court of India in the matter of Samira KohlivsDr.PrabhaManchanda&Anr on 16 January, 2008 Appeal (civil) 1949 of 2004, where the Apex Court said, “We therefore hold that in Medical Law, where a surgeon is consulted by a patient, and consent of the patient is taken for diagnostic procedure/surgery, such consent cannot be considered as authorisation or permission to perform therapeutic surgery either conservative or radical (except in life threatening or emergent situations). Similarly, where the consent by the patient is for a particular operative surgery, it cannot be treated as consent for an unauthorized additional procedure involving removal of an organ, only on the ground that such removal is beneficial to the patient or is likely to prevent some danger developing in future, where there is no imminent danger to the life or health of the patient.”